A muscular bag with a capacity of 8-12 Liters the horse’s stomach comprises around 10% of digestive tract volume. It is sealed off by sphincter muscles from the oesophagus and small intestine and the lower glandular part is separated from the upper squamous part by a demarcation called the margo plicatus. The glandular lining secretes hydrochloric acid and the enzyme pepsinogen. The acid chemically acts on proteins in food and also converts pepsinogen into the active form pepsin which digests proteins. The strongly acidic environment kills bacteria. The stomach wall is protected from acid attack by a lining of mucus secreted by the lining cells. Where the mucus protection is compromised the lining can be exposed to acid resulting in ulceration.

Food may spend as little as 15 minutes in the stomach when a large meal has been consumed, but an average time would be 30-45 minutes and longer if the horse is fasted. Compared to its body size the horse has the smallest stomach of all the domestic animals which is why small meals fed often are the most suitable. Very little nutrient absorbtion occurs in the stomach and most of that happens when food is passed further down the tract into the small intestine.

See also. E.G.U.S.

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